Hi John,
I turned my settings down to Low last night, and the mission loaded first time. I didn't know what the mission was about really, and when it loaded, there is quite a lot going on, its from an aircraft carrier and the frame rates were quite slow. Not sure what ur specs are without looking back, but i think mine are at the low end. Anyway, its loaded everytime since, and i actually completed the mission and its quite good, even at low settings. I've also made use of the LOW END environment that you can use that comes with YAP2.
Hope this helps.
Ste.
These are roughly my specs btw.

Intel core 2 duo CPU E6550 @ 2.33 GHz
2 gig RAM
Direct X 9.0c
Nvidia GS 8400 Graphics card